This has nothing to do with ABM's and frankly I don't know what all the excitement
is about, if you knew its flight path and knew where to stand you could shoot down
a Cruise Missile with a rifle. As for ICBM's, it seems to me that the only hope of
stopping one is to shoot it down during the boost phase, its got a huge infrared
signature, it's not moving very fast, it's fragile, one hit will destroy many warheads,
and you don't have to worry about decoys. So if you're really bothered by North Korea's
ICBM's (which the don't have) then just convince China to let you build the ABM
system on the China-Korea border.

Actually I think ICBM's are an obsolete means of delivering a warhead, it's like
spending a lot of money on a anti Zeppelin system, except that system would work.